The invention relates to a quantum dot preparation method, and more particularly to a ZnX, where X is S, Se, Te or a combination thereof, quantum dot preparation method.
ZnX quantum dot are semiconductor luminescent materials and usually used as phosphors. The energy gaps of ZnTe, ZnSe and ZnS are 2.39 eV, 2.82 eV and 3.68 eV respectively, and range from UV to visible light. By different concentrations or/and doping, the luminescent wavelengths of the phosphors can be tuned to predetermined wavelengths.
Conventional phosphors are prepared by high temperature treatment, such that phosphors grains grow and difficult to maintain at nanoscale (grain size<100 nm) or quantum dot (grain size<10 nm). From theoretical calculation and research, the luminescent efficiency of quantum dot is higher than bulk type, such that usage of phosphors has decreased, as does cost. Energy gap and luminescent wavelength of phosphors also can change with use of different grain sizes.
Small particle ZnX phosphors are usually prepared in aqua phase. For example, zinc salts such as ammonium zinc and surfactant are immersed in water, and NaS aqua solution is added drop by drop to obtain ZnS nano-particles. The resulting ZnS nano-particles, however, exhibit poor crystallization, frequent defects and low luminescent efficiency.
Recently, inorganic nano-particles have been formed in non-aqua phase at about 200˜400° C. A method for preparing ZnSe is described in “Bright UV-Blue Luminescent Colloidal ZnSe Nanocrystals”, Journal of Physical Chemistry B volume 102, number 19, 1998, issued to Margaret A. Hines and Philippe Guyot-Sionnest. In this method, diethyl zinc, hexadecylamine (HDA), trioctylphosphine (TOP) and Se powders are combined and heated to 300° C. to obtain ZnSe quantum dot. Although the ZnSe quantum dot have good crystallization, high luminescent efficiency and narrow particle distribution, diethyl zinc is flammable, unstable and expensive, so this method is not suitable for industry.
To resolve the described problems and obtain high luminescent efficiency ZnX quantum dot, there is a need for a better ZnX preparation method.